When you think about eating endangered species, you might imagine going to Chinatown to some secret restaurant — or to the ones operated by shadowy mobsters like in the 1990 comedy “The Freshman,” with Matthew Broderick and Marlon Brando. But if you order tuna in your neighborhood sushi restaurant, you too could be chewing the wrong thing — specifically, southern bluefin tuna (Thunnus maccoyii), a species classified as critically endangered by the International Union for Conservation of Nature and Natural Resources (IUCN).

This is one of the disturbing findings in a new paper in the open access journal PLoS ONE (hat tip to Tom Laskawy): “The Real maccoyii: Identifying Tuna Sushi with DNA Barcodes – Contrasting Characteristic Attributes and Genetic Distances.” (A note on the title’s wordplay: Maccoyii is the species name for the southern bluefin tuna, Thunnus maccoyii, and plays on an old expression meaning the “genuine article” — one that has a murky origin, says World Wide Words.) The authors and their collaborators collected 68 samples of tuna sushi from 31 restaurants in New York City and Denver. Whenever a tuna species was listed on the menu — “bluefin,” for example — the team ordered it. At restaurants that did not list the species on the menu, they went for “regular” (akami) and “fatty” (toro) tuna. If the menu didn’t list a species, they first asked the staff, “What kind of tuna is it?” and then “What species of tuna?” if the answer the to first query was not a valid species (“red tuna,” for example).

DNA analysis was performed on each sample to determine the species of fish, as well as to develop a “cytochrome c oxidase subunit I character-based key” to assist others in speciating tuna samples. Not surprisingly, they discovered numerous problems:

Vagueness and/or ignorance: 79% of the menus did not list any species of tuna. When staff was asked for a clarification, 32% of the clarifications were incorrect and 9% were not helpful (for example, answering with a non-existent species).

Mislabeling (or perhaps outright fraud): On numerous occasions, the restaurant staff told the customer that the fish was bluefin but served much cheaper bigeye tuna. (But all eight times when the menu specified bluefin tuna, bluefin was actually served.)

Hiding the unpleasant truth (or avoiding controversy): Several restaurants served northern bluefin tuna (T. thynnus) or the critically endangered southern bluefin tuna (T. maccoyii) despite a generic menu listing of tuna and a verbal clarification of “bigeye.” The authors postulate that selling the more expensive bluefin as a lesser grade tuna was a way of avoiding controversy, like the one that has been facing the Nobu chain of restaurants (previously covered at the Ethicurean and in links therein).

Revolting food: Five of the nine times they ordered “white tuna” from the menu, instead of receiving the expected albacore (T. alalunga), the researchers were served escolar (Lepidocybium flavorunneum). Escolar is banned for sale in Italy and Japan because the high level of wax esters in the fish’s flesh can cause serious side effects including “mild and rapid passage of oily yellow or orange droplets, to severe diarrhea with nausea and vomiting. The milder symptoms have been referred to as keriorrhea [i.e. flow of wax in Greek].” Although the fish can be sold legally in the U.S., Annex 2 of the FDA’s Hazard Analysis & Critical Control Point (HACCP) manual for operators recommends that “Escolar should not be marketed in interstate commerce.” So you might want to think twice before ordering “white tuna” when you next go out for sushi. (Wikipedia has more about escolar.)

Despite the article’s “gotcha” feeling, the research has very important implications for the survival of bluefin tuna. One of the prerequisites for a Convention on International Trade Endangered Species (CITES) listing is that the species needs to be identifiable in trade contexts so that violations can be reliably detected. The authors claim that their method reliably identifies all species of tuna, thus meeting the CITES prerequisite. Monaco has formally proposed that northern bluefin tuna be added to Appendix I of CITES during the 15th meeting of the Conference of the Parties to CITES that will be held in March 2010 in Doha, Qatar (PDF). And just last week, a majority of an FAO advisory panel agreed that the available evidence supports Appendix I listing (via La Vida Locavore). If listed, trade of the fish will be permitted “only in exceptional circumstances.”

The authors recommend that FDA modify the Seafood List, which recognizes appropriate “market names” for most of the seafood species sold in the U.S. Currently, the FDA allows seafood marketers to use the term “tuna” to describe all species of the genus (and several other fish outside of genus Thunnus). A requirement that bluefin tuna must be marketed as bluefin tuna would reduce uncertainty and protect against fraud.

At a more local level, sushi eaters can help the bluefin by not ordering any tuna sushi except when you have exceptional confidence that the restaurant can confirm that bluefin tuna is not being served.

Zorba — Thanks for the link to MBA’s sushi guide. It can be a useful tool when ordering sushi, but can be stymied by restaurants that don’t know exactly which fish they are serving — or restaurants that commit deliberate fraud. For example, the MBA guide lists Bigeye tuna as a “Good Alternative” but the researchers found several instances where the restaurant claimed that it was serving Bigeye but was actually serving Bluefin. This is a place where restaurants like Tataki are important (and under a lot of pressure). One of the requirements, in my view, of serving ‘sustainable sushi,’ is that they know exactly what they are serving and are honest about it, leading to a far lower probability of a menu listing of Bigeye resulting in Bluefin being served. Ideally, this rigor will travel up the supply chain and improve transparency for other buyers too.